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SubjectRe: [PATCH v2 2/3] Mutually exclude cpu online and suspend/hibernate
On 10/10/2011 06:03 PM, Srivatsa S. Bhat wrote:
> Don't allow cpu hotplug online operation and suspend/hibernate to run in
> parallel. If suspend/hibernate has already started, fail the cpu online
> operation.
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
>
> kernel/cpu.c | 10 ++++++++++
> 1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 12b7458..bc8c7d4 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -15,6 +15,7 @@
> #include <linux/stop_machine.h>
> #include <linux/mutex.h>
> #include <linux/gfp.h>
> +#include <linux/suspend.h>
>
> #ifdef CONFIG_SMP
> /* Serializes the updates to cpu_online_mask, cpu_present_mask */
> @@ -366,6 +367,14 @@ int __cpuinit cpu_up(unsigned int cpu)
> }
> #endif
>
> + /*
> + * Prevent cpu online and suspend/hibernate (including freezer)
> + * operations from running in parallel. Fail cpu online if suspend or
> + * hibernate has already started.
> + */
> + if (!trylock_pm_sleep())

Would it be better to hook into the suspend/hibernate notifiers and
use them to exclude cpu hotplug from suspend/hibernate, instead of
trying to take pm_mutex lock like this?
Peter, I remember you pointing out in another patch's review
(http://thread.gmane.org/gmane.linux.kernel/1198312/focus=1199087)
that introducing more locks in cpu hotplug would be a bad idea. Does that
comment hold here as well, or is this fine?

Anyways, I'll start working on that other implementation that hooks onto
the suspend/hibernate notifiers and see if that works out better.

> + return -EBUSY;
> +
> cpu_maps_update_begin();
>
> if (cpu_hotplug_disabled) {
> @@ -377,6 +386,7 @@ int __cpuinit cpu_up(unsigned int cpu)
>
> out:
> cpu_maps_update_done();
> + unlock_pm_sleep();
> return err;
> }
>
>


--
Regards,
Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Linux Technology Center,
IBM India Systems and Technology Lab



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